Crazy or Earpiece?

Once upon a time, when we saw someone walking down the street talking to themselves, we could be reasonably sure they were crazy. Then, along came the cell phone earpiece, and all bets were off. (I remember a stretch of time back in the 90s when I was repeatedly thrown: "Wow, that guy looks atypically polished and professional for a person suffering from paranoid psychosis. Oh... earpiece.")

Now, when I see someone walking down the street talking to themselves, I assume they're talking on an earpiece, but I'm occasionally surprised to discover that they're actually just crazy.

Which leads us to the question, how can one ever be sure? As the earpieces continue to shrink (converging, I suppose, on the teeny-tiny oh-so-chic embedded implants), visual cues vanish, and we're left to decide based solely on auditory and social cues.

I might speculate:

talking about taking the kids to soccer practice = earpiece

talking about the evil government agencies trying to steal our precious rag collections = crazy

wearing a business suit = earpiece

wearing a precious rag collection = crazy

But are these cues sure bets? What if there really are evil government agencies trying to steal our precious rag collections?* (And in light of the recent financial crisis, a lot of people in suits are looking pretty nutty. And rag collections are looking like comparatively savvy investments.)

So where does the truth lie? Is there a definitive Crazy-Versus-Earpiece Indicator? Oh! the post-modern existential angst of it all!

Any suggestions?

* Didn't recently declassified Justice Department memos, in fact, assert the executive branch's right to authorize Warantless Rag Acquisition?